It is known in the prior art to test integrated circuits using automatic testing equipment (ATE). ATE employ channel cards that include a plurality of pin electronics to test each channel/pin of an integrated circuit, which is referred to as a device under test (DUT). Standard in most pin electronics are a comparator circuit for comparing the input from the pin under test to an expected value, a driver circuit for testing a condition on a pin, an active load for simulating a changing signal, and a precision pin measurement unit (“PPMU”) for performing accurate pin tests of AC signals. Each of the four described elements is employed with a separate circuit. Each pin tester board can test at least one pin of the DUT. In some instances, a pin tester board is configured to test only a single pin of a device under test.
With the progression of technology, new elements are being added to integrated circuits that also need to be tested. For example, infrared sensors are becoming more commonly employed for a variety of purposes, including remote temperature sensing, spectroscopy, photography, and surveillance systems. Thus, there is a desire to incorporate the infrared sensors on the same silicon as other electrical elements. ATE does not have the capability to test infrared sensors using traditional pin tester boards and therefore, any chips that employ infrared sensors presently need to be disconnected from the ATE and attached to a separate infrared tester.
Currently infrared testers are tested with specialized equipment that use blackbodies. Blackbodies are radiation sources with a nearly ideal emissivity in the infrared spectrum that are used as the IR source to generate IR radiation which is defined by the temperature of the blackbody. In order to remove interference radiation emitted by other objects especially around the line of sight to the blackbody it is common to use a mechanical system that would periodically shutter the IR source with a covering/shutter positioned between the IR source and the IR sensor being tested. In order to test an IR sensor at two temperatures, two different blackbodies would need to be used, requiring complex mechanical manipulation.
An example in the prior art of testing an IR sensor is found in U.S. Pat. No. 7,119,326 to Logsdon et al. and is described with reference to FIG. 1. An IR sensor 125 is placed in an oven 110, which is heated to a first temperature. Two blackbodies 160, 165, heated to a second and a third temperature respectively, are mounted on a moveable track 130. The second and third temperatures of the blackbodies are both higher than the first temperature in the oven. IR sensor 125 is exposed to IR radiation from blackbody 160 through a window 120 in oven 110, which causes IR sensor 125 to produce a first output voltage, which is stored. Track 130 moves so that neither blackbody 160 or 165 is aligned with window 120, and a heating element attached to IR sensor 125 heats IR sensor until the first output voltage is reached again by applying a first power level to the heating element. The first power level is stored. Then track 130 moves to bring blackbody 165 in line with window 120. IR sensor 125 is exposed to IR radiation from blackbody 165, which causes IR sensor 125 to produce a second output voltage, and this voltage also is stored. Track 130 moves so that neither blackbody 160 or 165 is aligned with window 120, and the heating element attached to IR sensor 125 heats IR sensor until the second output voltage is reached again by applying a second power level to the heating element. The second power level is stored. The first and second power levels, measured as just described, can then be compared to first and second power levels measured in the same way for other IR sensors, and if the measured power levels are sufficiently similar, IR sensor 125 is then known to have the desired base output level and output sensitivity.
It is desirable to test IR sensors quickly and without onerous mechanical manipulations. It would be desirable to test IR sensors without the need to place them in ovens, which may then require time to reach or return to a target temperature. It would be further desirable to test IR sensors without needing to perform time-consuming mechanical manipulation of blackbodies or use a mechanical shuttering mechanism with moving parts. And it would be further desirable to test IR sensors directly according IR radiation emitted by an IR source, as opposed to using a heating element attached to the IR sensor, because in most desired applications, the IR sensor will be used to sense distant radiation and not heat applied directly to the IR sensor.